Renamed pppos_drop() → pppos_input_drop()
Renamed pppos_free_current_input_packet() → pppos_input_free_current_packet()
Moved pppos_output_last() after pppos_output_append()
Moved pppos_input_free_current_packet() before pppos_input_drop()
We actually allocated a pbuf chain only to iterate later the linked list
calling sio_write() for each pbuf, improved by calling sio_write() when
buffer is full and by recycling the pbuf, therefore only using one pbuf
for PPPoS output path.
Reworked pppos_write() and pppos_netif_output() to share more common
code into pppos_output_append() and pppos_output_last().
If PPP_INPROC_MULTITHREADED is true, then user does not what to use
the TCPIP API. Disabling the TCPIP API helps the user to understand
that PPP_INPROC_MULTITHREADED must not be used if he wish to use
the TCPIP API.
!NO_SYS users may now use as well the TCPIP API for PPPoS input data,
this way they can disable PPP_INPROC_MULTITHREADED and run pppos_input()
inside the lwIP thread, which fixes, at least for them, all the
threading issues related to PPP_INPROC_MULTITHREADED.
If PPP_INPROC_MULTITHREADED is not enabled, we can free unfinished
RX pbuf from the pppos_disconnect() function because pppos_input()
is running in the same context. Thanks to the pppos->open flags we
now only need to free remaining pbuf in the disconnect function
if PPP_INPROC_MULTITHREADED is not enabled.
Don't process input data if PPPoS is closed, it helps using
pppos_input() from a different context to prevent pppos_input() to
modify PPPoS RX machine state on a closed PPPoS session. It also
prevents allocating pbuf (which are going to be tossed out by PPP core)
and parsing serial input on a closed session.
It only mitigates the fact that this function is actually NOT thread
safe in absolutely all cases, it does not fix it but it helps for a low
cost.
For example user application should never call pppos_input() while
pppos_connect() or pppos_listen() is currently running because both of
them are freeing any input pbuf left over from the last session before
resetting the PPPoS state, they really have to to prevent pbuf leaks.
We cannot fix that easily because we don't have spinlock with an
irqsave/irqrestore helper for IRQ contexts. Mutex cannot be used in
interrupt contexts (or again, with an IRQ mutex helper).
We are going to improve the documentation on this point.
PPPoS was actually not thread safe, pppos_input() can be called from
lwIP user port at any time, whatever the PPP state is. It might even be
called during pppos_connect() and pppos_listen(), this is quite unlikely
the port do that but nothing prevent the user to since we document
pppos_input() as being thread safe.
Added a mutex if PPP_INPROC_MULTITHREADED is set and ensure pppos_input()
is safe in regard to other pppos_* functions.
pppos_create() can be called whether the modem is ready to process the
PPP session since pppos_create() does not start the PPP session anymore,
moved the advise from pppos_create() to ppp_open().
We only need to keep track of existing PPPoS interfaces if PPPoS
is not the only enabled protocol.
PPP CORE does not have callbacks pointers for all PPPoS callbacks
which should actually be required for PPPoS (VJ config, asyncmap, ...),
there is too much callbacks to create and PPPoS must be kept light,
especially for users who are only using PPPoS.
But there is a drawback, PPP CORE does not know which
lower protocols it is talking to thanks to the abstraction,
therefore if PPPoS is enabled as well as PPPoE or PPPoL2TP there
might be situation where PPP CORE calls pppos_ config functions
on interfaces which are NOT PPPoS one. This is very unlikely to
happen because protocols not supported by PPPoE or PPPoL2TP are
disabled at LCP/IPCP negotiation but we are better safe than sorry.
So we check if passed PPP pointer to PPPoS configuration functions
is a PPPoS interface by checking against a linked list of existing
PPPoS interfaces.
